1. Field of the Invention
The present invention relates to an electrical connector for electrically connecting an electronic package such as a land grid array (LGA) chip with a circuit substrate such as a printed circuit board (PCB), and particularly to a connector with reliable resilient beams.
2. Description of the Prior Art
Land grid array (LGA) electrical connectors are widely used in the connector industry for electrically connecting LGA chips to printed circuit boards (PCBs) in personal computers (PCs). As described in “Nonlinear Analysis HelpsDesign LGA Connectors” (Connector Specifier, February 2001, pp. 18-20), the LGA connector mainly comprises an insulative housing and a multiplicity of terminals. The housing comprises a multiplicity of terminal passageways defined therein in a generally rectangular array, for interferentially receiving corresponding conductive terminals. Due to the very high density of the terminal array in a typical LGA chip, the LGA chip need to be precisely seated on the LGA connector to ensure reliable signal transmission between the terminals and the LGA chip. Means for accurately attaching the LGA chip to the LGA connector are disclosed in U.S. Pat. Nos. 5,967,797 and 6,132,220.
Referring to FIG. 3, a conventional connector 6 comprises a substantially rectangular housing 60 and a multiplicity of conductive terminals 62 received therein. The housing 60 comprises four raised sidewalls 61, and a flat base 63 disposed between the four raised sidewalls 62. The base 63 and the sidewalls 61 cooperatively define a space therebetween for receiving an LGA chip 7 therein. The base 63 defines a multiplicity of terminal passageways 630 for receiving the terminals 62 therein. A resilient first arm 611 extends from one sidewall 61 into the base 63. Two spaced resilient second arms 612 extend from one adjacent sidewall 61 into the base 63. Each of the first and second arms 611, 612 is cantilever from the inner face of the corresponding sidewalls 61. A first space 610 is defined between the first arm 611 and the sidewall 61, and a second space 613 is defined between the second arm 612 and the adjacent sidewall 61. The first and second arms 611, 612 can generate resilient in respective space. The first arm 611 defines a first incline surface 611A at a distal end thereof, and the second arm 612 defines a second incline surface 612A at a distal end thereof. The first and second incline surface 611A, 612A can guide the LGA chip 7 on the base 63 to engage the terminals 62 received in the base 63.
In assembly, when the LGA chip 7 is placed in the base 63 of the housing 60, the LGA chip 7 engages the first incline surface 611A of the first arm 611 and the second incline surfaces 612A of the second arms 612 before engaging with the first and second arms 611, 612. Then the first and second arms 611, 612 generate resilient forces in respective spaces 610, 613 to hold the LGA chip 7. Thus the first and second arms 611, 612 cooperatively secure the LGA chip 7 on the connector 1. As a result, mechanical and electrical engagement between the terminals 61 and corresponding leads (not shown) of the LGA chip 7 is attained.
However, when the LGA chip 7 is received in the base 63, with two sides of the LGA chip 7 always pressing the first and second arms 611, 612 respective, a counterforce respectively presses upon the inner sides of the first and the second arms 611, 612 of the housing 60 to make the first and second arms 611, 612 deform all the time. Because the first and second arms 611, 612 are cantilever structure and they connect the respective sidewalls 61 respective only one end. Thus, after using for a long time, the first and second arms 611, 612 will crack from their respective ends connecting the sidewalls 61. If this happens, the LGA chip 7 can not secure between the sidewalls 61 reliably, and some terminals 61 received in the base 63 may not fully engage with the corresponding leads of the LGA chip 7. Uniform engagement between the terminals 61 and the corresponding leads of the LGA chip 7 is destroyed, and even open electrical circuits are formed therebetween. Thus, reliability of mechanical and electrical engagement between the terminals 61 and the corresponding leads of the LGA chip 7 is decreased.
Therefore, a new electrical connector which overcomes the above-mentioned problems is desired.